2) riscv_seL4: This BSP assumes it runs with support of seL4 microkernel, and it runs in Supervisor mode (on another core). seL4 application would allocate and map memory for it from its untyped memory (userspace), before off-loading it to another core.

To run it with seL4, you need to get seL4-rtems project first, configure it, but before building seL4 two shell variables have to be exported so that seL4 can know about where/which RTEMS image to load.